Pseudodielectric functions of InGaAs alloy films grown on InP

We present room-temperature pseudodielectric function spectra 〈e〉 of InxGa1−xAs films grown on (100) InP by solid-source molecular-beam epitaxy. A wet-chemical etching procedure is used to remove overlayers and obtain the best approximation to the bulk dielectric responses e of the films. By line shape fitting, we determined the x dependences of the E1 and E1+Δ1 critical-point energies and that of the Δ1 bowing parameter. The results are in good agreement with the predictions of a universal tight-binding model.